<button class="test_share">测试地址</button>
<div id="aaa"></div>
<div class="m-input-row">
    <textarea id="content" class="form-control m-fb-content" rows="8" placeholder="请输入反馈意见,我们会以消息形式回复您的建议或意见,改进用户体验,谢谢!"></textarea>
    <span class="m-textarea-num">0字</span>
</div>
<script src="//cdn.bootcss.com/jquery/1.12.1/jquery.js"></script>
<script type="text/javascript" charset="utf-8">


    // 判断是否IOS设备
    var isIOS = /(iPhone|iPod|iPad|ios)/i.test(navigator.userAgent);
    if(isIOS){
        // 检测粘贴
        document.getElementById('content').addEventListener('paste', function(){
            setTimeout(function() {
                var length = $('#content').val().length;
                $('.m-textarea-num').text(length + '字');
            }, 500);

        });
        // 检测复制
        document.getElementById('content').addEventListener('copy', function(){
            var length = $('#content').val().length;
            alert('2------' + length);
            $('.m-textarea-num').text(length + '字');
        });

    }
    $('.m-fb-content').on('keyup', function() {
        var length = $(this).val().length;
        alert('3------' + length);
        $('.m-textarea-num').text(length+'字');
    });

</script>